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Bi-Directional Alternator Fan
Posted by: jazzworkerbee ()
Date: May 18, 2020 01:59PM

Does anyone have experience with bi-directional alternator fans? I am upgrading to a 12SI alternator and my stock fan is nearly toast. There's a bi-directional fan sold on ebay that is cheaper than buying a NOS stock fan and assuming I can find an aluminum pulley, it might dress up the engine bay a bit. Alas, my experience is almost nil, so I'm asking for a bit of advice.

Thank you,

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

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Re: Bi-Directional Alternator Fan
Posted by: MattNall ()
Date: May 18, 2020 03:40PM

For that price try it!

MODERATOR
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Re: Bi-Directional Alternator Fan
Posted by: jazzworkerbee ()
Date: May 18, 2020 04:45PM

Tempted. I'll need to find a pulley. My stock unit is a little out of round, but appears to be 3 inches. When I have a little time this evening, I'll search for an aluminum, v-groove that's as close to 3 inches as possible.

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

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Re: Bi-Directional Alternator Fan
Posted by: The Stig ()
Date: May 18, 2020 04:47PM

I have run one and it worked. The question though is why not just get a stock one?

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Re: Bi-Directional Alternator Fan
Posted by: jazzworkerbee ()
Date: May 18, 2020 04:57PM

For starters, I want to make sure that the new, 12SI is cooled properly and I haven't been able to find a NOS fan/pulley that wasn't ridiculously expensive or almost as trashed as the one I have. The v-groove on mine is full of nicks and I figured that installing a new one would would be faster and easier. I have been told that aluminum pulleys track better, will run quieter than steel, keep the belt from flipping and help it last longer.

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

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Re: Bi-Directional Alternator Fan
Posted by: Vairismo ()
Date: May 18, 2020 05:03PM

Does a 12 series alternator back half mate with the Corvair alternator front half?
I thought the Corvairs were a 10 series size. I could be misremembering or just guessing, but still would like the answer. Thanks

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Re: Bi-Directional Alternator Fan
Posted by: jazzworkerbee ()
Date: May 18, 2020 05:09PM

Yes, it does, though I'll have to modify the stabilization bracket. Took forever to unfreeze the screws on the housing. I don't think it had ever been taken apart since it was new in 1965. Super rusty in there!

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

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Re: Bi-Directional Alternator Fan
Posted by: joelsplace ()
Date: May 18, 2020 06:39PM

The only alternators I've seen that were marked 12SI were physically bigger and wouldn't work but I've read a lot claiming they are the same size. The only thing I can conclude is the 12SI was made in 2 different physical sizes or the ones I saw were marked incorrectly.

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Bi-Directional Alternator Fan
Posted by: The Stig ()
Date: May 18, 2020 06:41PM

I have installed dozens of the 12SI in vairs over the years. I prefer them as they are smooth and look more like stock vs the ribbed 10SI.

Great source of info:
[www.madelectrical.com]



Edited 1 time(s). Last edit at 05/18/2020 06:42PM by The Stig.

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Re: Bi-Directional Alternator Fan
Posted by: old Jerry ()
Date: May 18, 2020 06:43PM

I run a bidrectional alternator fan on my reverse rotation 4.3 in my 66 Corvair.

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Re: Bi-Directional Alternator Fan
Posted by: jazzworkerbee ()
Date: May 18, 2020 07:06PM

That site was super helpful when I was trying to learn about this modification.

For those of you who are using a 12SI, how did you modify the stabilization bracket? If you have pictures, I’d greatly appreciate it!

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

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Re: Bi-Directional Alternator Fan
Posted by: 66vairman ()
Date: May 19, 2020 08:26AM

Years ago I found a site on the 10DN, 10SI, 12SI alternators.

The 10DN fan for GM cars or Corvair (reverse rotation) is only capable of providing adequate cooling up to 85Amps! When GM created the 12SI they modified the front housing AND fan to improve cooling so the amperage rating could be increased.

The 12SI fan (besides being the wrong rotation for a Corvair) won't work as efficiently with a 10DN or 10SI housing (if it will even fit).

Yes you see modified 10SI alternators rated at 100Amps and they will provide that, but not for extended periods because the cooling is inadequate (unless your only drive in cool weather, or don't exceed 85 Amps in demand).

GM designed the alternator to have adequate cooling even at elevated underhood temperatures during the summer in places like Arizona. So yes in cooler environments you can get away with less alternator cooling capacity. As the saying goes "Yes you can, no you shouldn't".

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Re: Bi-Directional Alternator Fan
Posted by: joelsplace ()
Date: May 19, 2020 04:22PM

An alternator on a Corvair is going to have much cooler air than in any other application since the others all sit behind a radiator. The Corvair alternator cooling air will be very close to ambient.

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Bi-Directional Alternator Fan
Posted by: deltadave ()
Date: May 23, 2020 05:18PM

Hey guys I saw this thread and ordered a fan. I got it a few days ago and installed it today. Was a good deal at $17

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Re: Bi-Directional Alternator Fan
Posted by: jazzworkerbee ()
Date: May 26, 2020 05:22PM

So the fan and pulley finally arrived. All in all, it was about $65 between the donor alternator, bi-directional fan, pulley and connectors. Now to bend the support bracket. I was hoping for a few images from others who have done this mod with the 12SI, but no dice. Looks like I'll be dusting off the torch and hammer! Can't start the engine yet without the connectors though. Should be here tomorrow, but I've been hearing that for about 4 days now...

Daniel

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

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Re: Bi-Directional Alternator Fan
Posted by: MattNall ()
Date: May 26, 2020 05:45PM

0.125"is plenty stiff

MODERATOR
Sea Mountain, between Charleston Harbor and Coos Bay! SW Oregon Coast
Click HERE for My Website...Click HERE for My TechPages!
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Re: Bi-Directional Alternator Fan
Posted by: jazzworkerbee ()
Date: May 26, 2020 06:03PM

I may need a little context. Are you saying that the pulley looks too large? I’m having some clearance issues with what I believe is the oil temp sensor, but that’ll be solved when I install my Offenhauser oil pan that has one integrated. Or, at least, that’s what I think it is...

Daniel Atkinson
Tacoma, WA
65 Turbocharged Corsa

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Re: Bi-Directional Alternator Fan
Posted by: joelsplace ()
Date: May 26, 2020 06:08PM

.125"?
A stock Corvair doesn't have an oil temperature sender. The aftermarket oil pans often have a place for one but don't come with them because they don't know what gauge you will be using.
You are probably looking at the oil pressure switch?

Joel
Northlake, TX
5 Ultravans, 114 Corvairs and counting...

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Re: Bi-Directional Alternator Fan
Posted by: wittsend ()
Date: May 26, 2020 06:13PM

Curious if anyone has adapted a Japanese alternator specifically from a Honda engine having a reverse rotation? BTW, these typically have internal fans.

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Re: Bi-Directional Alternator Fan
Posted by: American Mel ()
Date: May 26, 2020 07:01PM

joelsplace Wrote:
-------------------------------------------------------
> .125"?
> A stock Corvair doesn't have an oil temperature sender. The aftermarket oil pans often have a place for one but don't come with them because they don't know what gauge you will be using.
> You are probably looking at the oil pressure switch?


Oil Pressure in an Oil Pan ? ? ? confused smiley
What kind of car are you thinking of Joel?

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WA. state, 1 mile south of the Canadian border,
I am not at the end of the world, but you can see it from here.
Have; '66 Monza Coupe - 140, 4-spd. Daily driver beater
'67 Monza Vert. - 140, 4-spd. Daily driver beater
'67 A/C Moredoor Monza
Have had; '61 Monza coupe, '62 Monza Wagon, '63 Spyder, '65 Corsa
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non-vair
'04 Dodge Cummins Quad Dualy, approaching 400K
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